Part I. Quantum Chemical Methods: Theory and Computation in the Study of Molecular Structure.- Coupled-Cluster and Configuration-Interaction Approaches to Quasidegeneracy.- Noniterative Coupled-Cluster Methods for Excited Electronic States.- Excited State Self-consistent Field Theory using Even-tempered Primitive Gaussian Basis Sets.- Practicable Factorized TDLDA for Arbitrary Density- and Current-Dependent Functionals.- Inequalities Relating the Elements of the Second-Order Reduced Density Matrix.- Strutinsky\'s Shell-Correction Method in the Extended Kohn-Sham Scheme: Application to the Ionization Potential, Electron Affinity, Electronegativity and Chemical Hardness of Atoms.- Generalized Diabatic Study of Ethylene Isomerism.- Part II. Relativistic and Heavy-Element Systems: Progress with BERTHA: a Relativistic Atomic and Molecular Structure Package.- Generalized RECP Accounting for Breit Effects: Uranium, Plutonium and Superheavy Elements 112, 113, 114.-P,T-Parity Violation Effects in Polar Heavy-Atom Molecules.- QED Calculation of Heavy Multicharged Ions with Account for Correlation, Radiative and Nuclear Effects.- Quantum Calculation of Cooperative Muon-Nuclear Processes: Discharge of Metastable Nuclei During Negative Muon Capture.- Computer Simulations in Heavy Particle Collisions.- Part III. Complexes and Clusters: Study of Interaction Abilities Using an Energy Partitioning Scheme in Some Water Clusters.- Ab initio van der Waals Potential Energy Surfaces. Application to Complexes of Bromine Molecule with Helium Atoms.- One-Electron Pseudo-Potential Investigation of Na(3p2P)Arn Clusters: Electronically Excited Isomers and Emission Spectra.- Understanding Chemical Reactions Involving Non-Adiabatic Transitions: Predissociation of the Electronically Excited Li-HF Complex.- Density Functional Studies of Noble Metal Clusters. Adsorption of O2 and CO on Gold and Silver Clusters.- Three-Gold Cluster as Proton Acceptor inNonconventional Hydrogen Bonds O-H...Au and N-H...Au.- Molecular Modelling of Metal Complexes with Open d-Shell.- Part IV - Complex Systems: Ab-initio Gutzwiller Method: First Application to Plutonium.- Ab-initio Quantum Diffusion in Quasicrystals.-Towards Nanostructured Materials: an Example of Boron Nanotubes.- Stochastic Optimization Methods for Protein Folding.- Index